Internal combustion engine exhaust system

ABSTRACT

An exhaust system for an internal combustion engine having two banks of cylinders by which pulses of exhaust gas are alternately directed to a diverter subassembly. The diverter subassembly, which is located in the muffler, includes a perforated gas decelerator chamber which divides each pulse of exhaust gas between two exhaust outlets and causes a low pressure wave to occur in the exhaust system to enhance scavenging of a subsequent pulse of exhaust gas and thereby improve engine performance and mileage. The muffler further includes one or more cores and may or may not include a dead air space chamber to provide attenuation and tonal balance to the exiting exhaust gas.

RELATED APPLICATIONS

[0001] This application claims priority to a U.S. provisional patentapplication serial No. 60/291,585, filed May 16, 2001, titled “InternalCombustion Engine Exhaust System,” which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates generally to exhaust systems. Moreparticularly, the invention relates to an exhaust muffler for amulti-cylinder internal combustion engine.

[0004] 2. Description of the Related Art

[0005] Generally, vehicle manufacturers design exhaust systems to complywith sound attenuation and emission requirements. However, performanceengines used in vehicles such as sports cars are often designed tomaximize power output. The maximum power output often occurs at higherengine speeds. At these high speeds, exhaust system backpressure canlimit the operational envelope of the performance engine. A significantsource of the backpressure in the conventional exhaust system is amuffler.

[0006] The muffler design further changes the exhaust sound by way ofrestriction, absorption, or reflection methods alone, or with theircombination. As the exhaust gas is passed through the muffler, the soundwave energy associated with the exhaust gas is converted into heat andis dissipated. The muffler accomplishes this task with the use of metalplates, tubes, insulation, and/or chambers with a series of holes orperforations along with one of the three methods mentioned above.Typical OEM designs use restriction type mufflers which force theexhaust gas through a long arduous path, often including a chamberand/or reversing the direction of the gas flow. Restriction mufflerdesigns maximize their sound deadening ability at the significant costof reducing engine performance and fuel economy.

[0007] An example of an absorption method is a muffler design that sendsthe exhaust gases through a chamber by way of at least one straightthrough pipe that is perforated and wrapped with insulating material,for example, steel wool or fiberglass. The selection of chamber size andwhether the design will incorporate baffles will dictate the advantagesand disadvantages presented by the selected design. For example, if achamber is selected with a diameter slightly greater than the throughpipe, the sound attenuation will be minimal; however, minimal backpressure will be introduced into the exhaust system. In designs that usea much larger chamber than the straight through pipe, the soundattenuation will be increased, however, an increase in back pressurewill be incurred. With this design, as the exhaust gasses enter thelarge chamber, they expand and slow down dramatically whereby they dwelllonger in the insulating insulation, and thus absorb more noise. Thelarger chamber gently tapers back into the smaller size of the exhaustpipe. Reflective mufflers utilize absorption principles in conjunctionwith reflection to minimize noise by colliding out of phase sound wavesto cancel each other.

SUMMARY OF THE INVENTION

[0008] The systems and methods of the present invention have severalfeatures, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this invention as expressed bythe claims that follow, its more prominent features will now bediscussed briefly. After considering this discussion, and particularlyafter reading the section entitled “Detailed Description of thePreferred Embodiments” one will understand how the features of thisinvention provide several advantages over traditional scheduling methodsand systems.

[0009] One aspect is a muffler for receiving alternating pulses ofexhaust gas from a multi-cylinder engine. The muffler comprises ahousing and a gas decelerator chamber located substantially within thehousing. The gas decelerator chamber aligns alternating pulses ofexhaust gas onto a flow splitter, wherein the flow splitter divides thealternating pulses of exhaust gas between a first exhaust outlet and asecond exhaust outlet, and wherein the two exhaust outlets direct thedivided pulse of exhaust gas away from the flow splitter. In anembodiment, the muffler further includes cores located substantiallywithin the housing and connected to and in flow communication with theexhaust outlets, wherein the cores swirl the divided pulse of exhaustgas.

[0010] Another aspect is an exhaust system of a multi-cylinder enginethat comprises a plurality of exhaust ports which are split between afirst group and a second group, wherein the first group and the secondgroup each discharge a pulse of exhaust gas from the engine and amuffler. The muffler comprises a housing, a diverter subassembly locatedsubstantially in the housing and comprising a perforated gas deceleratorchamber, wherein the diverter subassembly aligns the pulse of exhaustgas from the first group and the second group onto a flow splitter inthe perforated gas decelerator chamber, wherein the flow splitter islocated obliquely to the direction of exhaust gas flow so as todistribute the pulse of exhaust gas between a first exhaust outlet and asecond exhaust outlet. In an embodiment, the muffler further includes aplurality of cores located substantially in the housing and connected toand in flow communication with the first and second exhaust outlets,wherein each core comprises perforations configured to swirl thedistributed pulse of exhaust gas as it travels through each core.

[0011] Another aspect is a method for processing exhaust gases from amulticylinder engine, wherein a pulse of exhaust gas is produced in acylinder of the multicylinder engine and processed by a muffler. Themethod comprises routing the pulse of exhaust gas in a flow path fromthe cylinder to one of two exhaust inlets of the muffler, wherein thetwo exhaust inlets alternate in their collection of subsequentdischarges of the pulse of exhaust gas, dividing a portion of the pulseof exhaust gas into two portions of exhaust gas with a perforated flowsplitter, and expelling both portions of exhaust gas from the mufflerand into the atmosphere.

[0012] Still another aspect is a resonator configured to connect with anoriginal equipment manufacturer (OEM) exhaust system and therebyattenuate exhaust noise. The resonator comprises a housing, wherein thehousing connects upstream of an OEM muffler and a diverter subassemblylocated substantially within the housing. The diverter subassemblycomprises a first inlet pipe and a second inlet pipe connected to and inflow communication with the OEM exhaust system, a gas deceleratorchamber connected to and in flow communication with the first and secondinlet pipes, wherein the alignment of the first and second inlet pipesdirects the pulse of exhaust gas onto a flow splitter in the gasdecelerator chamber, wherein the flow splitter is located obliquely tothe flow direction of the pulse of exhaust gas and divides the pulse ofexhaust gas, and a first outlet pipe and a second outlet pipe connectedto and in flow communication with the gas decelerator chamber, whereinthe two outlet pipes direct the divided pulse of exhaust gas away fromthe flow splitter and to the OEM muffler.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a bottom plan view showing an exhaust system accordingto a preferred embodiment of the invention.

[0014]FIG. 2 is a perspective view of a muffler assembly in accordancewith the preferred embodiment of the invention.

[0015]FIG. 3 is a cut-away top perspective view of the muffler assemblyin accordance with the preferred embodiment of the invention.

[0016]FIG. 4 is a top perspective view of a diverter subassembly that isa component of the muffler assembly shown in FIG. 3.

[0017]FIG. 5A is a top perspective view of a gas decelerator chamberthat is a component of the diverter subassembly shown in FIG. 4.

[0018]FIG. 5B is a bottom perspective view of the gas deceleratorchamber that is a component of the diverter subassembly shown in FIG. 4.

[0019]FIG. 6 is a top perspective view of one embodiment of a core thatis a component of the muffler assembly shown in FIG. 3.

[0020]FIG. 7 is a top perspective view of an alternate embodiment of thediverter subassembly that is a component of the muffler assembly shownin FIG. 3.

[0021]FIG. 8 is a bottom plan view showing an exhaust system accordingto an alternate embodiment of the invention.

[0022]FIG. 9 is a top perspective view of a resonator and an OEM mufflerfrom the exhaust system shown in FIG. 8.

[0023]FIG. 10 is a top perspective view of a diverter subassembly thatis a component of the resonator shown in FIG. 9.

[0024]FIG. 11 is a cut-away top perspective view of an alternateembodiment of the invention, wherein the cores extend to the end of themuffler assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Preferred embodiments of the present invention will now bedescribed with reference to the accompanying figures, wherein likenumerals refer to like elements throughout. The terminology used in thedescription presented herein is not intended to be interpreted in anylimited or restrictive manner simply because it is being utilized inconjunction with a detailed description of certain specific preferredembodiments of the present invention.

[0026] Traditionally, internal combustion engines employ exhaust systemsto convey the exhaust gas from the engine's cylinder to the ambientenvironment. The journey begins at the engine cylinder that incorporatesintake and exhaust ports and valves for ingress and egress to thecylinder. Fresh air mixed with fuel enters the engine cylinder throughthe intake port where it is subsequently compressed by a piston andignited. A rapid expansion of the compressed fuel and air occurs,thereby forcefully moving the piston in the opposite direction to thecompression stroke. Once the expansion is complete, the exhaust valveopens to allow the combustion by-products or gas to exit the enginecylinder through the exhaust port and enter an exhaust pipe. In the caseof a four-stroke design, a valve is utilized to open or close theexhaust port. The exhaust gas expelled from the engine cylinder, afterpassing through the exhaust port, enters an exhaust pipe.

[0027] The exhaust pipe is designed to direct the exhaust gas towardsthe rear of the vehicle and commonly utilizes bends and curves toaccomplish this goal. The exhaust gas, after passing through the exhaustpipe, is typically fed into a muffler prior to its expulsion into theatmosphere to dissipate, or “muffle,” unwanted noise originating in thecombustion process. The muffler design will significantly affect theaudible noise level or sound of the engine. A manufacturer can attenuateor change the sound of the engine in their selection of a muffler designso as to not only meet governmental noise requirements but also for theengine to exhibit a pleasing sound to the ear.

[0028] Depending on the design of the exhaust system, including themuffler, backpressure will occur, which impedes the free flow of exhaustgases along the exhaust system's entire length. For example, in afour-stroke engine, the piston pushes the exhaust gases out of thecylinder and into the exhaust system. If the back pressure in theexhaust system is reduced; the piston requires less force to expel theexhaust gases from the engine cylinder and thus increases theperformance and efficiency of the engine. The performance of an engineis measured by the engine's generation of, for example, horsepower andtorque over the entire rpm operating range. Generally, less backpressurewill enhance the performance of the engine, or more specifically theengine's production of horsepower and torque will increase along with anincrease in its efficiency and a corresponding decrease in the engine'sfuel consumption.

[0029] Customization of exhaust components, such as mufflers, by usersis common in the aftermarket. Customization allows the user tore-optimize the characteristics of their vehicle so as to maximize theirown satisfaction. A successful customization leads to not only personalsatisfaction of accomplishment, but also a feeling of attachment to thevehicle. Often, the replacement of a component made by the originalequipment manufacturer (OEM) with an aftermarket part does not live upto expectations and will not be easily reversible once it is completed.This can lead to the user incurring additional costs to reverse themodification.

[0030] In the case of exhaust systems, incorporation of aftermarketcomponents often requires cutting and welding of the OEM exhaust system.Exhaust pipes or other parts of the exhaust system are cut toincorporate a new muffler. Thus, the level of financial risk being takenby the user and difficulty in reversing the modification are increased.Furthermore, modifying an OEM exhaust system to improve performance isfurther complicated by space limitations along the undercarriage of thevehicle.

[0031]FIG. 1 is an undercarriage plan view of an automobile 16 showingan exhaust system 18 according to the preferred embodiment of theinvention. An internal combustion engine 20 has two cylinder banks 22,24 in an opposed arrangement. The two cylinder banks 22, 24 consist of aplurality of cylinders 26, 28, respectively. In the embodiment of theinvention shown in FIG. 1, the two cylinder banks 22, 24 comprise fourleft and four right cylinders in the plurality of cylinders 26, 28. Eachof the two cylinder banks 22, 24 have fixedly attached a cylinder head30, 32 which forms a plurality of combustion chambers (not shown) withineach plurality of cylinders 26, 28. Each cylinder head 30, 32incorporates at least one of a plurality of intake ports (not shown) andat least one of a plurality of exhaust ports 34 for ingress and egressto the plurality of cylinders 26, 28. The intake ports are connected toan intake system (not shown) where fresh air mixed with fuel enters theplurality of engine cylinders 26, 28 where it is subsequently compressedby a plurality of pistons (not shown) into the plurality of combustionchambers (not shown) and ignited. A rapid expansion of the compressedfuel and air occurs, thereby forcefully moving the plurality of pistonsin the opposite direction to the compression stroke.

[0032] The ignition of the compressed fuel and air occurs in analternating sequence whereby one of the plurality of cylinders 26transmits a pulse of exhaust gas followed by the transmission of anotherpulse of exhaust gas from one of the plurality of cylinders 28. In theembodiment shown in FIG. 1, this sequence depends on the engine designand continually repeats during the operation of the internal combustionengine 20. Once the rapid expansion of the compressed fuel and air iscomplete, one of the plurality of exhaust ports 34, which is in flowcommunication with the ignited engine cylinder 26, 28, opens to allowthe combustion by-products or pulse of gas to exit through the cylinderhead 30, 32 and into a plurality of primary exhaust pipes 36, 38.

[0033] The plurality of primary exhaust pipes 36, 38 have a plurality ofinlet ends (not shown) which are connected to the plurality of exhaustports 34 to scavenge each pulse of exhaust gas from the plurality ofengine cylinders 26, 28. Each of the primary exhaust pipes 36, 38 areconfigured to be in flow communication with each of the cylinders 26, 28and are brought together into one of two collector chambers 40, 42 foreach of the two cylinder heads 30, 32. Each of the two collectorchambers 40, 42 is connected to and in flow communication with at leastone outlet end (not shown) of each plurality of primary exhaust pipes36, 38, wherein the two collector chambers 40, 42 alternate in theircollection of subsequent discharges of the pulse of exhaust gas from theinternal combustion engine 20.

[0034] The combination of pulses of exhaust gas in the preferredembodiment of the present invention increases the performance of theinternal combustion engine 20 by enhancing scavenging. Scavenging is theprocess of removing the exhaust gases from the cylinders. A properlyscavenged engine will run more efficiently, using less fuel to make morepower and lower emissions. In a four-stroke engine, this reduces theforce required by the piston to expel the pulse of exhaust gas from theplurality of cylinders 26, 28.

[0035] In another embodiment of the invention, the collector chambers40, 42 may take another form (not shown) in an exhaust system. For aneight-cylinder engine, this process could be an exhaust manifoldcombining the exhaust ports on each bank into an exhaust pipe for eachbank entering into a muffler.

[0036] In still another embodiment of the invention, the plurality ofcylinders 26, 28 each have their own equal length primary exhaust pipe(not shown). This means each primary exhaust pipe 36, 38 is routedbetween the plurality of exhaust ports 34 and the collector chambers 40,42 such that all of the plurality of primary exhaust pipes have the sameoverall length. Each plurality of primary exhaust pipes feeds into oneof the two collector chambers 40, 42 as opposed to manifolds asdiscussed above. The benefit to using equal length primary exhaust pipesis that the pulses of exhaust gas will not arrive at the same time ateach of the collector chambers 40, 42, which minimizes any interferencebetween the pulses.

[0037] Still referring to FIG. 1, in the preferred embodiment, the twocollector chambers 40, 42 are further connected to the muffler assembly48 by way of secondary exhaust pipes 44, 46. Once the exhaust gases passthrough the muffler assembly 48, they will enter one or more downstreamexhaust pipes 50, 52 on their way to being expelled into theenvironment. As illustrated in FIG. 1, the exhaust system 18 isprimarily symmetrical with respect to axis X-X. However, one who isskilled in the art will appreciate that the exhaust system 18 can bedesigned non-symmetrically to accommodate various undercarriage designfactors. These design factors may include, but are not limited to,incorporating a transverse engine, driveline configuration, axlelocation, spare tire location, and fuel tank location. In an alternateembodiment, the secondary exhaust pipes 44, 46 incorporate a pollutioncontrol device, for example a catalytic converter, upstream of themuffler assembly 48.

[0038] Now referring to FIG. 2, a perspective view of an externalhousing 54 of the muffler assembly 48 is shown. Each pulse of exhaustgas from one of the secondary exhaust pipes 44, 46 enters the externalhousing 54 through muffler inlets 56, 58. Thus, the muffler inlets 56,58 form flow conduits between the secondary exhaust pipes 44, 46 and themuffler assembly 48. Likewise, muffler outlets 60, 62 providepassageways for each pulse of exhaust gas to exit the external housing54.

[0039] In another embodiment, a single muffler outlet (not shown)provides the passageway for each pulse of gas to exit the externalhousing 54. In this embodiment, the single muffler outlet is centeredbetween the illustrated locations of the muffler outlets 60, 62 in FIG.2. Alternatively, the single muffler outlet is shifted away from thecentered location. The location of the single muffler outlet can beadvantageously selected for a specific application to the automobile 16.In embodiments with the single muffler outlet, one or more downstreamexhaust pipes 50, 52 are attached thereto.

[0040] The operation of one embodiment of the muffler assembly 48 may beunderstood upon reference to FIG. 3, which is a cut-away top perspectiveview of a muffler assembly 48 incorporating aspects of the invention.Inside the external housing 54 is a diverter subassembly 64, cores 66,68, and a dead air space chamber 63. The diverter subassembly 64 and theplurality of exhaust cores 66, 68 are in flow communication through afirst baffle plate 65. While the plurality of exhaust cores 66, 68 andthe dead air space chamber 63 are in flow communication through a secondbaffle plate 67.

[0041] Still referring to FIG. 3, the diverter subassembly 64 receiveseach pulse of exhaust gas by way of one of the plurality of mufflerinlets 56, 58, each connected to and in flow communication with one ofthe secondary exhaust pipes 44, 46. The exhaust gas flows into thediverter subassembly 64 where the pulse of exhaust gas is bisectedbetween the cores 66, 68. While the pulse of exhaust gas passes throughthe diverter subassembly 64, the gas near the periphery of the pulseexpands through an array of perforations 90 in the diverter subassembly64. The pulse of exhaust gas expands through the perforations 90dissipating a portion of the exhaust gas's sound energy into thesound-absorbing material, which may be placed between the diverter 64and the external housing 54.

[0042] As shown more clearly in FIG. 4, the diverter subassembly 64 maycomprise a gas decelerator chamber 70, two inlet pipes 72, 74, and twooutlet pipes 76, 78. The two inlet pipes 72, 74 and the two outlet pipes76, 78 are in flow communication with the gas decelerator chamber 70.The two inlet pipes 72, 74 receive the pulses of exhaust gas from theplurality of muffler inlets 56, 58. In an alternate embodiment, the twogas inlet pipes 72, 74 and the two gas outlet pipes 76, 78 are integralwith gas decelerator chamber 70. In this embodiment, the length of thegas accelerator chamber 70 is extended so as to include the length ofthe gas inlet and outlet pipes shown in FIG. 4. Thus, the extended gasaccelerator chamber 70 alone forms the diverter subassembly 64.

[0043] Now referring to FIGS. 5A-5B, which are top and bottomperspective views of the gas decelerator chamber 70, respectively, acomponent of the diverter subassembly 64 from FIG. 4 is shown. Exhaustinlet 82 is in flow communication with inlet pipe 72; and exhaust inlet80 is in flow communication with inlet pipe 74. The exhaust inlets 80,82 are aligned to direct the pulse of exhaust gas travelling from thetwo gas inlet pipes 72, 74 onto a flow splitter 84 which may be integralto the gas decelerator chamber 70. The exhaust inlets 80, 82 form anacute angle so that each of the two gas inlet pipes 72, 74 are in linewith the flow splitter 84. The outer surface of the flow splitter 84 isprimarily concave with the inner surface being primarily convex. Theflow splitter 84 is located obliquely to the flow direction of the pulseof exhaust gas to divide each pulse of exhaust gas between two exhaustoutlets 86, 88. The two exhaust outlets 86, 88 direct each distributedpulse of exhaust gas away from the flow splitter 84 forming alow-pressure zone (not shown) in the wake of the pulse of exhaust gas.The low-pressure zone preferentially travels back up the exhaust systemcomponents towards the plurality of exhaust ports 34 to scavenge thesubsequent pulse of exhaust gas.

[0044] Still referring to FIGS. 5A-5B, one advantageous embodiment ofthe gas decelerator chamber 70 is provided with an array of perforations90 extending therethrough. It is to be understood, however, thatlouvers, slots, or other substantially equivalent communication meanscan be provided in place of the perforations 90 to enable expansion ofthe exhaust gas in the gas decelerator chamber 70 into thesound-absorbing material between the decelerator chamber 70 and theexternal housing 54. In an alternate embodiment shown in FIG. 8, theperforations 90 extend along the entire diverter subassembly 64.Furthermore, in alternate embodiments, the size of the perforations 90can be varied along the surface of the gas decelerator chamber 70.

[0045] In one embodiment of the invention, the gas decelerator chamber70 is fabricated by welding two perforated upper and lower halves 90together. In an alternate embodiment, the perforations are added oncethe gas decelerator chamber 70 is formed.

[0046] Returning to FIGS. 3, 4, and 5A-5B, the two exhaust outlets 86,88 are in flow communication with the cores 66, 68 via the two gasoutlet pipes 76, 78. As shown more clearly in FIG. 6, an embodiment ofthe cores 66, 68 have a cylindrical shape, although the illustratedcircular cross-section is not essential, and non-circular cross-sectionsmay be preferred in some embodiments. Formed in the cores 66, 68 is anarray of stamped, cup-shaped perforations 94. It is to be understood,however, that louvers, slots, holes, or other substantially equivalentcommunication means can be provided in place of the perforations 94. Forexample, the perforations 94 can be rectangular, cup-shaped, orhexagonal. Moreover, the perforations 94 can extend for the entirelength or for one or more portions of the cores 66, 68. Furthermore, inalternate embodiments, the size of the perforations 94 can be variedalong the length of the cores 66, 68.

[0047] In one embodiment, each perforation has an arcuate concave outersurface formed by lancing the core 66, 68 and forcing a section thereofinwardly within the interior of the core 66, 68. In this embodiment, theresulting perforation has a cup-shape with one end of the cup-shapedperforation open and one end closed (FIG. 6, Section A-A). Thecup-shaped perforations 94 are preferably formed in a series of helicalrows extending along the full length of the core 66, 68 with the closedends of the cup-shaped perforations 94 facing in the same direction suchthat the bisected pulse of exhaust gas from the diverter subassembly 64first engages the closed ends of each cup-shaped perforation 94. Thecup-shaped perforations 94 create a swirling turbulence that reflectsthe exhaust sounds around within the cores 66, 68 thereby furtherattenuating and dissipating the sound waves.

[0048] Now referring again to FIG. 3, while the bisected pulse ofexhaust gas passes through the cores 66, 68 it also passes over thecup-shaped perforations 94. To enhance sound attenuation, a sounddeadening material 69, such as layers of glass, composite, or steel woolmaterial, may be added around the cores 66, 68 and inside the spaceformed between the first and second baffle plates 65, 67 and theexternal housing 54. The sound deadening material may be wrapped aroundboth cores 66, 68 or around each individual core 66, 68.

[0049] Still referring to FIG. 3, once the bisected pulse of exhaust gasexits the cores 66, 68, the exhaust gas enters the dead air spacechamber 63. The dead air space chamber 63 allows the bisected pulse ofexhaust gas to recombine prior to being expelled to the atmosphere. Inan alternate embodiment shown in FIG. 11, the dead air space chamber 63and the second baffle plate 67 are omitted, and the cores 66, 68 extendto the exhaust outlets 60, 62.

[0050] Engine performance tests were completed on a Ford SVT Cobra R®using the exhaust system 18 constructed in accordance with oneembodiment of this invention. Dynamometer results demonstrated anincrease in maximum horsepower from 359.5@77.0 MPH to 375.6@80.0 MPH.The increase in performance caused by the muffler assembly 48 translatesinto more roll-on power, which increases the user's ability to passtraffic at highway speeds and increase fuel economy. In addition,incorporation of the muffler assembly 48 overcomes the Ford SVT Cobra R®engine's lack of a strong, throaty rumble being emitted from its stockexhaust system. Dynamometer tests were also performed on a ToyotaTundra® truck with the muffler assembly 48 installed. These testsmeasured an increase in maximum horsepower from 224 to 240. It will beappreciated that the vehicles that would benefit from incorporating themuffler assembly 48 into their exhaust systems are not limited to thevehicles described above.

[0051] In one embodiment of the invention, as illustrated in FIG. 1, theautomobile 16 is shown with the muffler assembly 48 incorporated into anoriginal equipment manufacturer (OEM) exhaust system. A feature of thispreferred embodiment is that most of the components of the OEM exhaustsystem (not shown) are retained so as to maintain the integrity of theOEM exhaust system. The installation of the muffler assembly 48 merelyrequires the removal of the OEM muffler (not shown) which does notrequire any permanent modification to the automobile 16.

[0052] An alternate embodiment of the exhaust system according to theinvention is shown in FIGS. 8 and 9. This embodiment illustrates aresonator 96 added to an OEM exhaust system 100 without removing an OEMmuffler 98. A resonator in an exhaust system will further attenuate theexhaust noise. Often resonators are similar to the straight throughmuffler except they usually incorporate insulating material. Resonatorscan be located forward or aft of the muffler in the exhaust system. Oneresonator design is called a Hehnholtz resonator. A Helmholtz resonatoris similar to a straight through muffler without any insulating materialsince it depends on reflecting to cancel the sound waves.

[0053] The resonator 96 is incorporated into the exhaust system 100upstream of the OEM muffler 98. As shown in FIG. 10, the resonator 96includes a diverter subassembly 64 as described above. In thisembodiment, after the pulse of exhaust gas passes through the divertersubassembly 64, it exits the resonator 96 where it re-enters the OEMexhaust system upstream of the OEM muffler 98.

[0054] The embodiments described herein provide sufficient soundattenuation of the exhaust gases while increasing the engine'sperformance characteristics. Furthermore, the muffler designs modify thetonal qualities of the exhaust sound so as to be pleasing to the user.This design is also easily incorporated into an OEM exhaust system.

[0055] The invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiment is to be considered in all respects only as illustrative andnot restrictive and the scope of the invention is, therefore, indicatedby the appended claims rather than the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed is:
 1. An exhaust system for a multi-cylinder engine, the system comprising: a plurality of exhaust ports, each in communication with a cylinder of the engine to discharge a pulse of exhaust gas; a plurality of primary exhaust pipes, each having an inlet end and an outlet end, wherein the inlet end is connected to one of the plurality of exhaust ports to scavenge the pulse of exhaust gas; two collector chambers, each connected to and in flow communication with at least one outlet end of the plurality of primary exhaust pipes, wherein the two collector chambers alternate in their collection of subsequent discharges of the pulse of exhaust gas from the engine; two secondary exhaust pipes, each connected to and in flow communication with one of the collector chambers; and a muffler housing, wherein the muffler housing encloses: a diverter subassembly, wherein the diverter subassembly comprises: a first inlet pipe and a second inlet pipe connected to and in flow communication with the two secondary exhaust pipes; a gas decelerator chamber connected to and in flow communication with the first and second inlet pipes, wherein the alignment of the first and second inlet pipes directs the pulse of exhaust gas onto a flow splitter in the gas decelerator chamber, wherein the flow splitter is located obliquely to the flow direction of the pulse of exhaust gas and divides the pulse of exhaust gas; and a first outlet pipe and a second outlet pipe connected to and in flow communication with the gas decelerator chamber, wherein the two outlet pipes direct the divided pulse of exhaust gas away from the flow splitter forming a low-pressure zone in the wake of the pulse of exhaust gas, and wherein the low-pressure zone preferentially travels back up the exhaust system as a reflected negative wave to scavenge the subsequent pulse of exhaust gas; a plurality of cores connected to and in flow communication with the first and second outlet pipes, wherein each core is perforated or louvered to swirl the divided pulse of exhaust gas as it travels through each core; a dead air space chamber connected to and in flow communication with the plurality of cores; and a plurality of muffler outlets connected to and in flow communication with the dead air space chamber and configured to expel the exhaust gases out of the muffler housing and into the atmosphere.
 2. An exhaust system according to claim 1, wherein the flow splitter has a convex shape and is formed by an inner surface of the gas decelerator chamber.
 3. The exhaust system according to claim 2, wherein the gas decelerator chamber is perforated.
 4. The exhaust system according to claim 3, wherein the gas decelerator chamber has substantially an X shape.
 5. The exhaust system according to claim 3, further comprising a baffle plate located between the diverter subassembly and the plurality of cores, wherein the baffle plate substantially isolates a first chamber formed between the muffler housing and the diverter subassembly from a second chamber formed between the muffler housing and the plurality of cores.
 6. A muffler for receiving alternating pulses of exhaust gas from a multi-cylinder engine comprising: a housing; and a gas decelerator chamber located substantially within the housing, wherein the gas decelerator chamber aligns alternating pulses of exhaust gas onto a flow splitter, wherein the flow splitter divides the alternating pulses of exhaust gas between a first exhaust outlet and a second exhaust outlet, and wherein the two exhaust outlets direct the divided pulse of exhaust gas away from the flow splitter.
 7. The muffler according to claim 6, further comprising a plurality of cores located substantially within the housing and connected to and in flow communication with the exhaust outlets, wherein the plurality of cores swirl the divided pulse of exhaust gas.
 8. The muffler according to claim 7, wherein at least a portion of a surface of the gas decelerator chamber comprises perforations to allow the alternating pulses of exhaust gas to also flow through the surface and into the housing.
 9. The muffler according to claim 8, wherein the perforations extend along a substantial portion of the length of the gas decelerator chamber.
 10. The muffler according to claim 9, wherein the flow splitter is located obliquely to both flow directions from the exhaust inlets.
 11. The muffler according to claim 10, wherein the flow splitter has a convex shape and is formed by an inner surface of the gas decelerator chamber.
 12. The muffler according to claim 8, further comprising an insulating material wrapping one or more of the plurality of cores.
 13. The muffler according to claim 12, wherein a surface of at least one of the plurality of cores comprises perforations, wherein the perforations allow the divided pulse of exhaust gas to flow through the surface and into the housing.
 14. The muffler according to claim 13, wherein the perforations are cup-shaped.
 15. The muffler according to claim 13, wherein the cup-shaped perforations are arranged in helical rows around the surface of at least one of the plurality of cores.
 16. The muffler according to claim 15, wherein the cup-shaped perforations extend along the length of at least one of the plurality of cores.
 17. A muffler design according to claim 8, further comprising a dead air space chamber located substantially within the housing and connected to and in flow communication with the plurality of cores.
 18. The muffler design according to claim 8, further comprising a baffle plate located between the gas decelerator chamber and the plurality of cores, wherein the baffle plate substantially isolates a first chamber formed between the muffler housing and the gas decelerator chamber from a second chamber formed between the muffler housing and the plurality of cores.
 19. The muffler design according to claim 18, further comprising a second baffle plate located between the plurality of cores and the dead air space chamber, wherein the second baffle plate substantially isolates the second chamber from the dead air space chamber.
 20. An exhaust system of a multi-cylinder engine, the system comprising: a plurality of exhaust ports which are split between a first group and a second group, wherein the first group and the second group each discharge a pulse of exhaust gas from the engine; and a muffler, wherein the muffler comprises: a housing; and a diverter subassembly located substantially in the housing and comprising a perforated gas decelerator chamber, wherein the diverter subassembly aligns the pulse of exhaust gas from the first group and the second group onto a flow splitter in the perforated gas decelerator chamber, wherein the flow splitter is located obliquely to the direction of exhaust gas flow so as to distribute the pulse of exhaust gas between a first exhaust outlet and a second exhaust outlet.
 21. The exhaust system of claim 20, wherein the muffler further comprises a plurality of cores located substantially in the housing and connected to and in flow communication with the first and second exhaust outlets, wherein each core comprises perforations configured to swirl the distributed pulse of exhaust gas as it travels through each core.
 22. The exhaust system according to claim 21, further comprising a baffle plate located between the diverter subassembly and the plurality of cores, wherein the baffle plate substantially isolates a first chamber formed between the muffler housing and the diverter subassembly from a second chamber formed between the muffler housing and the plurality of cores.
 23. The exhaust system according to claim 22, wherein the perforations are cup-shaped.
 24. The exhaust system according to claim 23, wherein the cup-shaped perforations are arranged in helical rows around the surface of at least one of the plurality of cores.
 25. A method of processing exhaust gases from a multi-cylinder engine, wherein a pulse of exhaust gas is produced in a cylinder of the multi-cylinder engine and processed by a muffler, the method comprising: routing the pulse of exhaust gas in a flow path from the cylinder to one of two exhaust inlets of the muffler, wherein the two exhaust inlets alternate in their collection of subsequent discharges of the pulse of exhaust gas; dividing a portion of the pulse of exhaust gas into two portions of exhaust gas with a perforated flow splitter; and expelling both portions of exhaust gas from the muffler and into the atmosphere.
 26. The method of claim 25, further comprising swirling both portions of exhaust gas.
 27. A muffler comprising: a housing; means for splitting the pulse of exhaust gas with a perforated flow splitter mounted inside the housing; and means for expelling the split pulse of exhaust gas into the atmosphere.
 28. An automobile comprising: a chassis; a multi-cylinder engine attached to the chassis and having two cylinder heads, each containing at least one cylinder; and a muffler housing, wherein the muffler housing comprises a gas decelerator chamber located substantially within the muffler housing, wherein the gas decelerator chamber aligns alternating pulses of exhaust gas onto a flow splitter, wherein the flow splitter divides the alternating pulses of exhaust gas between a first exhaust outlet and a second exhaust outlet, and wherein the two exhaust outlets direct the divided pulse of exhaust gas away from the flow splitter.
 29. A method of manufacturing a muffler for a multi-cylinder engine, the method comprising: connecting a diverter subassembly to a plurality of cores, wherein the diverter subassembly is substantially perforated and has two inlet pipes and two outlet pipes, wherein each inlet pipe is aligned to direct a pulse of exhaust gas onto a flow splitter, wherein the flow splitter is located obliquely to the flow direction of the pulse of exhaust gas and divides the pulse of exhaust gas between the two outlet pipes, wherein the two outlet pipes direct the divided pulse of exhaust gas away from the flow splitter and into the plurality of cores, wherein the plurality of cores are perforated to swirl the divided pulse of exhaust gas; connecting the plurality of cores to a dead air space chamber, wherein the dead air space chamber forms a common manifold for the divided pulse of exhaust gas; and installing the gas decelerator chamber, the plurality of cores, and the dead air pace chamber within a muffler housing.
 30. The method of manufacturing a muffler according to claim 29, further comprising inserting a baffle plate between the diverter subassembly and the plurality of cores, wherein the baffle plate substantially isolates a first chamber formed between the muffler housing and the diverter subassembly from a second chamber formed between the muffler housing and the plurality of cores.
 31. A resonator configured to connect with an original equipment manufacturer (OEM) exhaust system and thereby attenuate exhaust noise, the resonator comprising: a housing, wherein the housing connects upstream of an OEM muffler; and a diverter subassembly located substantially within the housing, wherein the diverter subassembly comprises: a first inlet pipe and a second inlet pipe connected to and in flow communication with the OEM exhaust system; a gas decelerator chamber connected to and in flow communication with the first and second inlet pipes, wherein the alignment of the first and second inlet pipes directs the pulse of exhaust gas onto a flow splitter in the gas decelerator chamber, wherein the flow splitter is located obliquely to the flow direction of the pulse of exhaust gas and divides the pulse of exhaust gas; and a first outlet pipe and a second outlet pipe connected to and in flow communication with the gas decelerator chamber, wherein the two outlet pipes direct the divided pulse of exhaust gas away from the flow splitter and to the OEM muffler.
 32. The resonator according to claim 31, wherein at least a portion of a surface of the gas decelerator chamber comprises perforations which allow the pulse of exhaust gas to also flow through the surface and into the housing. 